Problem: Solve for $r$ : $17 = r + 2$
Subtract $2$ from both sides: $ \begin{eqnarray} \\ \hphantom{17 {- 2}} &\hphantom{=}& \hphantom{r} \\ 17 &=& r + 2 \\ \\ {-2} && {-2} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 17 {- 2} &=& r \\ \end{eqnarray} $ Simplify. $ r = 15$